Mining fractures in overlying strata is the key factor to achieve water-conservation mining, safe coal mining under water, efficient gas drainage and accurate ecological restoration in mining subsidence areas. In order to accurately clarify the evolution and distribution characteristics of overburden mining fractures, based on the key strata theory and the mining degree of overburden failure, the contact state at the top of the fracture zone in the middle of the goaf is analyzed from non-contact separation to point surface, line surface and surface to surface contact after the overburden failure reaches the full mining degree, and expounds that the reason for the saddle shape of water conducting fracture zone is the same as the formation mechanism of surface subsidence. The overburden failure characteristics are analyzed by similar simulation, and it is pointed out that the permanent mining fractures are mainly concentrated in the overburden structure at the boundary of the working face. Meanwhile, the shear deformation test of hard rock (sandstone) in overburden fracture zone shows that rock damage is positively correlated with the shear stress, and the maximum subsidence deflection of rock layer under corresponding overburden load is 1% of the thickness of the rock layer when breaking. Combined with the similarity simulation and the deduced formula of maximum deflection under the critical condition of broken rock stratum, the consistency is verified, and the stability condition of overburden structure are analyzed. According to the strata separation rate and mining fracture distribution characteristics, the fracture zone is divided into four horizontal areas (namely original rock fracture area, tensile fracture area, structural void area and void compaction area), and a method for judging the regional range of fracture zone is proposed. The engineering practice is carried out, and the results show that the net gas drainage amount of directional boreholes arranged in the structural fracture area can reach 5.52 m³/min, which can effectively extract the pressure relief gas in the goaf, and verify the rationality of fracture zoning based on the mining degree of overburden failure.

overburden failure, overburden structure, mining fractures, fracture zone, regional distribution